Process for preparing esters

ABSTRACT

A PROCESS FOR PRODUCING ESTERS WHICH INVOLVE REACTING A DIBASIC ORGANIC ACID WITH AN ORGANIC HALIDE IN ADDED WATER CONTAINING A BASIC SALT OF A SULFONIC ACID HAVING FROM 12 TO 20 CARBON ATOMS.

United States Patent 3,686,274 PROCESS FOR PREPARING ESTERS Russell G. Hay, Gibsonia, and John G. McNulty and William L. Walsh, Glenshaw, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa. No Drawing. Filed Apr. 20, 1970, Ser. No. 30,243

. Int. Cl. C070 69/34, 69/80 US. Cl. 260-475 R 14 Claims ABSTRACT OF THE DISCLOSURE A process for producing esters which involve reacting a dibasic organic acid with an organic halide in added water containing a basic salt of a sulfonic acid having from 12 to 20 carbon atoms.

This invention relates to a process for preparing esters.

In our copending application Ser. No. 30,244, filed concurrently herewith and assigned to the same assignee as the present application, we defined and claimed a process for preparing esters by reaction of selected dibasic organic acids with selected organic halides in added water containing a sulfonic acid having from 12 to 20 carbon atoms. Although satisfactory yields of esters are produced by such process, unfortunately the esters so obtained are contaminated with bromine or chlorine and impart a color thereto. Since these esters find great utility as plasticizers, wherein color bodies are undesirable, it is apparent that to the extent they contain color bodies they tend to become less commercially attractive. We have now found that when the reaction between the dibasic organic acid and the organic halide is carried out in added water containing a basic salt of a sulfonic acid having from 12 to 20 carbon atoms, the halogen content of the ester produced is materially reduced.

The first reactant employed herein to produce the desired ester are dibasic acids that include dibasic organic acids such as aliphatic straight and branched chain dibasic acids having from four to 22 carbon atoms, preferably from four to 18 carbon atoms, straight and branched chain olefinic dibasic acids having from four to 22 carbon atoms, preferably from four to 18 carbon atoms, cyclic dibasic acids having from five to 22 carbon atoms, preferably from five to 18 carbon atoms, and aromatic dibasic acids having from eight to 22 carbon atoms, preferably from eight to 18 carbon atoms; and polybasic acids having from four to 22 carbon atoms, preferably from four to 18 carbon atoms. Specific examples of dibasic acids that can be employed include aliphatic straight and branched dibasic acids, such as succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, methylsuccinic acid, dimethylsuccinic acid, methyladipic acid, etc.; straight and branched olefinic dibasic acids, such as maleic acid, fumaric acid, methylmaleic acid, dimethylmaleic acid, ethylmaleic acid, methylfumaric acid, dimethylfumaric acid, chloromaleic acid, dichloromaleic acid, glutarconic acid, etc.; cyclic dibasic acids, such as cyclohexane dicarboxylic acid, cyclopentane dicarboxylic acid, cyclododecane dicarboxylic acid, etc.; aromatic dibasic acids, such as ortho-phthalic acid, nitrophthalic acid, tetrachlorophthalic acid, etc., and polybasic acids, such as tricarballylic acid, aconitic acid, citric acid, etc.

Although we have defined the first reactant as being a dibasic acid, it is apparent that wherein an anhydride of a defined dibasic acid exists it can be used in place of the dibasic acid. In fact, as the data hereinafter show, in the specific examples we have employed an anhydride as a first reactant.

To react with the dibasic acids defined above to produce the desired ester in accordance with the process 3,686,274 Patented Aug. 22, 1972 defined and claimed herein there must be employed an organic halide selected from the group consisting of primary straight and branched chain alkyl halides having from one to 30 carbon atoms, preferably from one to 22 carbon atoms; secondary straight and branched chain alkyl halides having from one to 30 carbon atoms, preferably from one to 22 carbon atoms; primary cyclic halides having from four to 22 carbon atoms, preferably from four to 12 carbon atoms; secondary cyclic halides having from three to 22 carbon atoms, preferably from three to 12 carbon atoms, primary straight and branched chain olefinic halides having from three to 22 carbon atoms, preferably from six to 22 carbon atoms; and secondary straight and branched chain olefinic halides having from three to 22 carbon atoms, preferably from six to 22 carbon atoms. Specific examples of organic halides that can be used herein are the same as those defined in application Ser. No. 333,624, filed Dec. 26, 1963, starting on page 4, line 21 thereof and ending on page 18, line 16, which organic halides are incorporated herein 'by reference. Of the organic halides defined above, we prefer to employ alkyl halides, particularly primary straight and branched chain alkyl halides. Of the alkyl halides, we prefer alkyl chlorides and alkyl bromides. Although we prefer to employ the organic acids and the organic halides in approximately stoichiometric amounts, the molar proportions thereof can vary from about 10:1 to about 1:10.

In order that the dibasic acid be made to react with the organic halide herein water must be added to the reaction system. The molar ratio of water to the organic halide reactant defined above can be from about 1:1 to about :1, but preferably is about 2:1 to about 40:1.

To increase the amount of ester produced and to reduce the halogen impurity associated therewith, it is imperative that there also be present in the reaction zone a basic salt of a sulfonic acid having from 12 to 20 carbon atoms, preferably from 14 to 18 carbon atoms, wherein the basic portion thereof, as an ionization constant, has a pK, basicity of about 10- to about 10- preferably about 10- to about 10- Specific examples of sulfonic acid salts that can be employed are ammonium normal dodecylbenzenesulfonate, pyridine normal dodecylbenzenesulfonate, piperidine normal dodecylbenzenesulfonate, quinoline normal dodecylbenzenesulfonate, zinc normal dodecylbenzenesulfonate, aluminum normal dodecylbenzenesulfonate, ammonium normal decylbenzenesulfonate, pyridine normal decylbenzenesulfonate, zinc normal decylbenzenesulfonate, ammonium normal octylbenzenesulfonate, pyridine normal octylbenzenesulfonate, zinc normal octylbenzenesulfonate, ammonium normal dodecanesulfonate, pyridine normal dodecanesulfonate, zinc normal dodecanesulfonate, ammonium normal octadecanesulfonate, pyridine normal octadecanesulfonate, zinc normal octadecanesulfonate, ammonium normal eicosanesulfonate, pyridine normal eicosanesulfonate, zinc normal eicosanesulfonate, ammonium 3 methyldodecanesulfonate, pyridine 3-methyldecylbenzenesulfonate, zinc 4- ethyloctylbenzenesulfonate, etc. By normal we mean linear. The amount of sulfonic acid salt required is at least about 0.05 percent by weight based upon the total reaction mixture, preferably from about 0.2 to about two percent by weight.

In carrying out the reaction, the reactants defined above, water and the defined sulfonic acid salt are merely brought together in any convenient manner. The temperature can be as low as about and as high as about 250 C., but preferably is about to about 200 C. At the low temperatures, the reaction proceeds slowly, while at the higher temperatures shorter reaction times are required and the production of alcohols corresponding to the organic halide and some olefins and a slight increase in ether are obtained. Pressures are not critical and any pressure is suitable, but in order to maintain water in the reaction zone, a pressure of at least about one hundred pounds per square inch gauge is preferred and pressures up to about 1000 pounds per square inch gauge can be used. The reaction time is similarly not critical and is dependent upon the other variables involved and on the amount of conversion desired. In general, a reaction time of about one minute to about 40 hours, preferably from about 15 minutes to about three hours can be used.

During the course of the reaction, an ester, hydrogen halide, water and some alcohol, ether and olefin are produced. The ester can be recovered from the reaction product in any convenient manner. For example, upon cooling, the reaction mixture resolves itself into an aqueous layer and an organic layer. Depending on the density of the organic product formed, the organic layer can be either the upper or lower layer. The two layers can be separated from each other in any convenient manner, for example, by decantation. The organic layer will contain the organic components and the same can be separated from each other in any suitable manner, for example, by distillation. The aqueous layer contains the water originally present, water that formed, unreacted organic acid and hydrogen halide. It is believed that the hydrogen halide complexes or in some manner attaches itself to the water. The complex exists as a liquid. The aqueous layer can be discarded, if desired, but in a preferred embodiment, the hydrogen halide and unreacted organic acid can be recovered by subjecting the aqueous layer to distillation at low pressures, for example, 100 millimeters of mercury, to remove substantially all of the uncomplexed water and organic acid overhead, after which the complex is subjected to distillation at an elevated pressure, for example, 75 pounds per square inch gauge, to remove substantially anhydrous hydrogen halide overhead.

The process defined herein can further be illustrated by the following. Into a 300-milliliter glass pressure reactor there was introduced an organic halide, an anhydride, water, a normal sulfonic acid alone, a salt of a normal sulfonic acid alone or a normal sulfonic acid with an ammonium salt. The glass was placed in a shielded cage and the contents were stirred by a magnetic stirrer. The contents of the glass reactor were raised to 170 C. and the pressure rose to 150 pounds per square inch gauge. After holding the contents of the reactor under these conditions for one hour, the reactor was permitted to cool to room temperature, opened and the contents were found to be present in two layers, an upper organic layer and a lower aqueous layer. The organic layer was analyzed by gas liquid chromatography to determine the product distribution. The organic ester product was obtained by distillation of the total organic layer. The bromine content of the ester product was determined by neutron activation analysis. The results obtained are tabulated below in Table I.

contaminated with 879 parts per million of broine. In each of Runs 2 and 3, wherein a basic salt of a' sulfonic acid falling within the defined basicity was used, a satisfactory yield of ester was obtained and the bromine impurity was reduced dramatically. In Run 4, wherein a basic salt of a sulfonic acid falling outside the defined range was used, a substantial reduction in bromine impurity was achieved, but the amount of ester produced was similar to that which would be obtained in its absence. Run 5 shows that the basic salt used need not be added as such but can be formed in situ.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for preparing an ester which comprises contacting a dibasic organic acid selected from the group consisting of aliphatic straight and branched chain dibasic acids having from four to 22 carbon atoms, straight and branched chain olefinic dibasic acids having from four to 22 carbon atoms, cyclic dibasic acids having from five to 22 carbon atoms and aromatic dibasic acids having from eight to 22 carbon atoms or a corresponding anhydride thereof with an organic halide selected from the group consisting of primary straight and branched chain alkyl halides having from one to 30 carbon atoms, secondary straight and branched chain alkyl halides having up to 30 carbon atoms, primary cyclic halides having from four to 22 carbon atoms, secondary cyclic halides having from three to 22 carbon atoms, primary straight and branched chain olefinic halides having from three to 22 carbon atoms and secondary straight and branched chain olefinic halides having from three to 22 carbon atoms in the presence of added water containing a basic salt of a sulfonic acid having from 12 to 20 carbon atoms, wherein the basic portion thereof, as an ionization constant, has a pK, basicity of about 10- to about 10- 2. The process of claim 1 wherein the K, basicity is in the range of about 10* to about 10- 3. The process of claim 1 wherein the basic salt is ammonium dodecylbenzenesulfonate.

4. The process of claim 1 wherein the basic salt is pyridine dodecylbenzenesulfonate.

5. The process of claim 1 wherein the amount of basic salt present is at least about 0.05 percent by weight based on the reaction mixture.

6. The process of claim 1 wherein the amount of basic salt present is from about 0.2 to about two percent by Weight based upon the total reaction mixture.

7. The process of claim 1 wherein said anhydride is phthalic anhydride.

8. The process of claim 1 wherein said organic halide is l-bromo octane.

TABLE I Grams of additive Mols charged Ammo- Parts Weight percent in product ofnium Sodium Pyridine Dodecyl- Ammoper mil- 1- Phthalic dodecyldodecyldodecylbenzenenium lion of Dioctyl bromo anbenzenebenzenebenzenesulfonic brobromine phthall-oc- Dioctyl Run No. octane hydride Water sulfonate sulfonate sulfonate acid mide in ester ate tanol Octenes ether The uniqueness of the present process is apparent from 9. The process of claim 1 wherein the molar ratio of a study of the above data. In Run No. 1 wherein the addiwater to organic halide is from about 1:1 to about 80:1. tive employed was solely normal dodecylbenzenesulfonic 10. The process of claim 1 wherein the molar ratio of acid the yield of ester was satisfactory but the same was water to organic halide is from about 2:1 to about 40:1.

6 11. The process of claim 1 wherein the reaction is 031- References Cited ried out at a tempeature of about 100 to about 200 C. UNITED STATES PATENTS 12. The process of claim 1 wherein the reaction is car- 2,903,477 9/1959 Hughes et aL ried out at a temperature of about 120 to about 200 C.

13. The process of claim 1 wherein the basic salt is ob- LEWIS GOTTS, Primary Examiner tained from a sulfonic acid and having from 12 to 20 L SKELLY Assistant Examiner carbon atoms and an ammonium salt.

14. The process of claim 1 wherein the basic salt is US. C1.X.R. obtained from normal dodecylbenzenesulfonic acid and 10 260.468 H, 468 K, 471 R, 75 N, 4 P, 485 R, 43 5 H, ammonium bromide. 435 4 5 N 

